Great Wall of China

History

The original walls were built to defend territories between feuding Chinese states. The walls were constructed using a long known technique of stomping ground between two boards. The result was a hard wall made of earth and stone able to withstand small attacks. In 221 B.C., Qin defeated the enemy states and created the Qin Dynasty. To defend his new territory from the Xiongnu attackers, Qin ordered the destruction of the state border walls and a new wall was to be constructed along the Chinese border.

Utilizing the original technology of stomping dirt between boards was again used during construction on the Great Wall of China. The Great Wall of China is actually a series of walls, which do not connect. The Xiongnu were able to go around the walls in attempts to attack, but they did deter and slow the attacks. Eventually, the Xiongnu attacks desisted and the construction of the Great Wall was halted. Construction resumed during the Ming Dynasty when Emperor Ming's army suffered defeat at the hand of the Mongolian Army. During this phase of construction, the Great Wall of China was built using brick and stone, resulting in wider, higher and stronger walls. In addition to stronger walls, watchtowers were introduced along the wall, so the army could communicate with each other. The watchtowers were installed on top of hills, so the signals could be seen from other watch towers.

Construction

The combined length of sections of the Great Wall of China stretches for over 5,550 miles. The sections of the Great Wall of China vary from 16-26 feet high, while the width of the wall varies from 16-19 feet. The strongest sections of wall surround Beijing to protect it from invasions. Portions of the wall have suffered major erosion as the wall is over 2,400 years old and are now is disrepair. The Great Wall of China even fended off Manchu invasions during the 1600's.

In 2007, the Chinese government, in an effort to preserve the Great Wall of China, restricted the number of tourists visting the Great Wall of China to 53,000 per day. For hundreds of years, scholars have written about being able to see the Great Wall of China from the moon. So far, no astronaut has acknowledged this claim, although it can been seen from low orbit.